(1) Field of the Invention
The present invention pertains to a surgical instrument that is constructed in an extremely small scale for use in microsurgery. In particular, the present invention pertains to a microsurgical instrument having a pair of operative surgical surfaces that are moved relative to each other in shearing or grasping procedures performed by the instrument, where the surgical instrument and its operative surgical surfaces are constructed by electric discharge machining.
(2) Description of the Related Art
Microsurgical instruments are those types of surgical instruments employed in performing surgical operations on extremely small and extremely delicate parts of the human anatomy, for example the tissues inside the human eye. There are many different types of microsurgical instruments. The more complex in construction and the most difficult to manufacture are microsurgical instruments that have at least one pair of operative surgical surfaces that move relative to each other in use of the instrument. By operative surgical surfaces what is meant is, for example, the opposed shearing surfaces of a scissors that have shearing edges that move across each other in a sheering operation performed by the instrument, or the opposed grasping surfaces of a forceps that move toward and away from each other in a grasping operation performed by the instrument. In the manufacturing of microsurgical instruments of this type, it is desirable that the scale of the instrument be as small as possible so that the introduction of the instrument to the surgical site is minimally invasive.
A typical microsurgical instrument is comprised of a manual handle that is similar in size and shape to a pen or pencil, which enables the instrument to be easily manipulated by the surgeon in one hand. An instrument head is secured to one end of the handle and the microsurgical forceps or a scissors tip projects from the instrument head. An example of this type of instrument is disclosed in U.S. Pat. No. 5,370,658, assigned to the assignee of the present invention and incorporated herein by reference.
Prior art microsurgical instrument tips of the type disclosed in the referenced patent often comprise a hollow, narrow tube projecting from the instrument head. A rod is received in the tube and the rod and tube are caused to reciprocate relative to each other in response to manual manipulation of some type of actuator on the instrument handle. The relative movement between the rod and tube operates the surgical instrument formed at the distal ends of the rod and tube. Where the surgical instrument is a forceps, the opposed jaws of the forceps are formed at the rod distal end and moving the tube over the rod or retracting the rod into the tube causes the forceps jaws to move toward each other. The reverse movements of the tube and rod cause the jaws to separate from each other. Where the surgical instrument is a scissors, one of the shear surfaces is formed at the distal end of the rod and the other shear surface is formed at the distal end of the tube. Moving the tube distal end toward the rod distal end causes the shear surfaces and their shearing edges to move toward and across each other.
As stated earlier, for microsurgical applications, the surgical instruments discussed above must be manufactured in an extremely small scale. In manufacturing the forceps discussed above, two pieces of wire stock would typically be ground down along their entire lengths until each piece was reduced to substantially half of its original thickness or width. Gripping surfaces would then be formed on the distal ends of the two pieces of wire stock by further grinding or cutting grooves across the previously ground surfaces of the wires. The two wire halves would then be welded or brazed together at their proximal ends and along an intermediate portion of their lengths. The thus formed forceps would then typically be polished.
In forming a scissors of the type discussed above, the scissor blade would first be cut from metal stock and one of the scissor blades would be welded or brazed to the distal end of the rod and the other of the scissor blades would be welded or brazed to the distal end of the tube. The operative surgical surfaces or the two shearing surfaces of the blades would then be ground forming shearing edges on the two surfaces. The rod and tube and the pair of blades attached thereto would then be polished to enhance their appearance.
The need for the final grinding step of the operative surgical surfaces of the instruments, i.e. the gripping surfaces of the forceps and the shearing surfaces of the scissors, limit the size to which a microsurgical instrument can be scaled. Due to the stresses exerted on the operative surgical surfaces of the instruments as the surfaces are ground, there must be a sufficient amount of material present in these areas of the instruments to withstand the grinding. Thus, the need to grind the material of the instrument tips to form the operative surgical surfaces of the microsurgical instruments limits the size to which the instruments can be reduced.